With the development of communication technologies, wireless communication technologies have developed from technologies such as Global System for Mobile Communications (GSM) or Code Division Multiple Access (CDMA) in their respective ways to Long Term Evolution (LTE) technologies. In order to meet market demands of various communication systems, the same data card is no longer applied to one type of communication system only, that is, a multi-mode data card integrated with a variety of communication systems has appeared on the market currently. With enhancement of functions of the data card and improvement of the transmission rate, requirements on the power of the data card are also increased. The demand of power of the data card is mainly concentrated in two operating modes, a standby mode and a data transfer mode. When the data card is in the standby mode, the corresponding transient current is about 5 mA to 10 mA; when data is transferred, the power is required to be relatively high, and the corresponding transient current is about 1.5 A to 2 A.
Existing data cards are mainly connected to computers via Universal Serial Bus (USB) interfaces, which are not only used as paths on which the data cards transfer data, but also used to supply power to the data cards. According to the USB 2.0 protocol standards and specifications, current which can be provided by a USB interface should not exceed 500 mA. The current provided by the USB interface can only satisfy power demands of single-mode data cards and some of multi-mode data cards, but can not satisfy power demands of other multi-mode data cards, and particularly, in particularly, can not satisfy the power demands of these multi-mode data cards during data transmission. Therefore, in implementation of functions of data cards, power of some of the data cards is supplemented by setting large energy storage capacitors in the data cards, and power of the other of the data cards is supplemented by setting batteries in the data cards.
Since the data cards are developed based on communication systems of mobile terminals, power-up and power-down processes of the data cards are similar to those of the mobile terminals. After a battery is added to a data card, a push-button switch is required to implement power-up and power-down operations of the data card. The addition of the push-button switch not only influences appearance of the data card, but also makes it is not simple and easy enough for a user to operate. In addition, after power-down of the current data card with the battery, because the battery is still connected to a function module of the data card, there is some static power consumption in the battery. If the data card is not used for a long time, electric quantity of the battery will be exhausted gradually, thereby shortening the battery life or damaging the battery.